For example, for supporting a heavy shaft inside a housing so that it may rotate freely, a self-aligning roller bearing with retainer such as for example, those disclosed in Japanese Patent Application Publication No. H 09-317760 (Patent Document 1) and in Japanese Utility Model Registration No. 2524932 (Patent Document 2), has conventionally been used. FIG. 16 to FIG. 19 show a first example of the conventional construction disclosed in Patent Document 1. This self-aligning roller bearing with retainer is configured with a plurality of spherical rollers 3 arranged so as to allow them to rotate freely between an outer ring 1 and an inner ring 2, which are concentrically combined. A retainer 4 controls the orientation and position of this plurality of spherical rollers 3.
A spherical concave shaped outer raceway 5 having a single center is formed on an inner peripheral surface of the outer ring 1. Moreover, a pair of inner raceways 6, which respectively oppose the outer raceway 5, are provided on both sides in the width direction (left-right direction in FIG. 17) of an outer peripheral surface of the inner ring 2. Furthermore, the plurality of spherical rollers 3 have a symmetrical shape (beer barrel shape) the maximum diameter of which is in the middle section of the length in the axial direction of the spherical rollers 3, and this plurality of spherical rollers 3 is provided in two rows between the outer raceway 5 and the pair of the inner raceways 6, being freely rotatable in each row. Furthermore, a radius of curvature of a generatrix of the rolling surfaces of the respective spherical rollers 3 is slightly smaller than that of the generatrixes of the outer raceway 5 and the inner raceways 6.
The retainer 4 is provided with one rim section 7 and a plurality of column sections 8. The rim section 7 is annular in shape, and is arranged between both rows of spherical rollers 3. Moreover, each of these column sections 8 is disposed in the axial direction of the outer ring 1 and inner ring 2 in a state where the base end sections of the column sections 8 are respectively joined to a plurality of positions at even intervals around the circumferential direction of the surfaces on both sides in the axial direction of the rim section 7. The end section of each column section 8 is a free end that is not joined with other sections. The portion between the column sections 8 that are co-adjacent to each other in the circumferential direction is a pocket 9 for holding each of the spherical rollers 3 so that they may rotate freely. Moreover, by having an outer peripheral surface of the rim section 7 closely opposed to the inner peripheral surface of the middle section of the outer ring 1, the position of the retainer 4 in the radial direction is determined (by outer ring riding). Furthermore, flange shaped outward rib sections 10 are respectively formed on the outer peripheral surfaces of both end sections of the inner ring 2 so that the respective spherical rollers 3 do not disengage outwards in the axial direction from the space between the inner peripheral surface of the outer ring 1 and the outer peripheral surface of the inner ring 2.
According to the self-aligning roller bearing with retainer constructed as described above, in the case where, for example, a rotation shaft is to be supported inside a housing, the outer ring 1 is fitted and fixed inside the housing, and the inner ring 2 is fitted and fixed outside the rotation shaft. When the inner ring 2 rotates together with the rotation shaft, the plurality of the spherical rollers 3 roll and allow this rotation. When the shaft centers of the housing and the rotation shaft are not matched, the inner ring 2 self-aligns inside the outer ring 1 (the central axis of the inner ring 2 tilts with respect to the central axis of the outer ring 1) to compensate this mismatch. In this case, since the outer raceway 5 is formed in a single spherical shape, even after compensating the mismatch, the plurality of spherical rollers 3 roll smoothly.
In the case of the first example of the conventional construction described above, the retainer 4 for holding both rows of spherical rollers 3 is integrated. By contrast, Patent Document 2 discloses a construction in which retainers 4a for holding both rows of spherical rollers 3 are made mutually independent as shown in FIG. 20. In the case of this second example of the conventional constriction too, the rib sections 10 are formed on the outer peripheral surfaces of both end sections of the inner ring 2 so that the respective spherical rollers 3 do not disengage outwards in the axial direction from the space between the inner peripheral surface of the outer ring 1 and the outer peripheral surface of the inner ring 2.
Moreover, in Patent Document 1, as shown in FIG. 21, there is disclosed a construction in which the outer peripheral surfaces of both end sections of the inner ring 2a have no rib sections as a result of connecting the end sections of the respective column sections 8a, which constitute the retainer 4b, by a connection section 11. In the case of this third example of the conventional construction, according to the engagement of the respective connection sections 11 and the end surfaces in the axial direction of the spherical rollers 3, the respective spherical rollers 3 are prevented from disengaging outwards in the axial direction from the space between the inner peripheral surface of the outer ring 1 and the outer peripheral surface of the inner ring 2.
Moreover, FIG. 22 shows a fourth example of a conventionally known self-aligning roller bearing with retainer. In the case of the construction of the fourth example, a floating guide ring 16 is provided between the inner peripheral surface of the rim section 7 and the outer peripheral surface of an intermediate section of the inner ring 2, the outer peripheral surface of the floating guide ring 16 is made to closely oppose the inner peripheral surface of the rim section 7 and the inner peripheral surface of the floating guide ring 16 is made to closely oppose the outer peripheral surface of the intermediate section of the inner ring 2, to position the retainer 4c in the radial direction (by inner ring riding). Furthermore, flange shaped outward rib sections 10 are respectively formed on the outer peripheral surfaces of both end sections of the inner ring 2 so that the respective spherical rollers 3 do not disengage outwards in the axial direction from the space between the inner peripheral surface of the outer ring 1 and the outer peripheral surface of the inner ring 2.
In the cases of the first to fourth examples of the conventional construction, improvements in the following points are needed in order to achieve higher speed of the rotation shaft.
First, in the cases of the first, second, and fourth examples shown in FIG. 17, FIG. 20, and FIG. 22, the rib sections 10 on the outer peripheral surfaces of both end sections of the inner ring 2, narrow the aperture area of the end section of the space between the inner peripheral surface of the outer ring 1 and the outer peripheral surface of the inner ring 2. Consequently, in the case where lubrication of the rolling contact portion between the rolling surfaces of the spherical rollers 3 and the outer raceway 5 and both inner raceways 6 is to be carried out by means of splash lubrication with oil-mist or oil-air, there is a disadvantage from the aspect of performing high speed operation, as the flow rate of the lubricant (lubrication oil) that enters into the above space is decreased. Furthermore, on assembling the respective spherical rollers 3 into the space, both of the rib sections 10 become an obstacle. Therefore, a notch for passing through the respective spherical rollers 3 needs to be formed in one portion of both of the rib sections 10, making processing of the inner ring 2 inconvenient, and the effect of preventing coming off becomes imperfect.
In the case of the third example of the conventional construction shown in FIG. 21, since the rib section is not present on the outer peripheral surface of both end sections of the inner ring 2a, the rib section does not narrow the aperture area of the end section of the space between the outer peripheral surface of the inner ring 2a and the inner peripheral surface of the outer ring 1. However, the connection section 11 provided for the retainer 4b narrows the aperture area of the end section of the space. Therefore, as is the case with the first, second, and fourth examples, the flow rate of lubricant (lubrication oil) that enters into the space decreases, resulting in a disadvantage for high speed operation.
Furthermore, in the case of the first and third examples of the conventional construction shown in FIG. 17 and FIG. 21, since the positions in the radial direction of the retainers 4a and 4b for holding both rows of spherical rollers 3 are determined according to the engagement of the outer peripheral surface of the rim section 7 with the inner peripheral surface of the outer ring 1, and in the case of the fourth example shown in FIG. 22, according to the engagement of the inner peripheral surface of the rim section 7 with the outer peripheral surface of the floating guide ring 16, there are disadvantages in achieving high speed operation of the rotation shaft due to the following points. Specifically, in the case of such construction, a relative speed (sliding velocity) between the outer peripheral surface and the inner peripheral surface of the outer ring 1, or between the inner peripheral surface of the rim section 7 and the outer peripheral surface of the floating guide ring 16 becomes greater, and friction at the engaging section between both these peripheral surfaces becomes greater as a result. This results in a greater amount of dynamic torque (rotational resistance) and heat being generated due to operation of the self-aligning roller bearing with retainer, which becomes a disadvantage in high speed operation.
Furthermore, there is a possibility of a greater amount of dynamic torque and heat being generated due to operation as a result of a difference in revolution speeds of both rows of spherical rollers 3. Specifically, when operating the self-aligning roller bearing with retainer, although in some cases the self-aligning roller bearing with retainer is operated in a state where both rows of spherical rollers 3 support the same amount of load when operating (under the same condition), in many cases the self-aligning roller bearing with retainer is operated in a state where the spherical rollers 3 in either one of the rows support a greater amount of load compared with the other row. As a result, the revolution speeds of both rows of spherical rollers 3 become different. In such cases, it is possible that the row of spherical rollers 3 with the higher revolution speed revolves while dragging the row of spherical rollers 3 with the lower revolution speed. Conversely, the row of spherical rollers 3 with the lower revolution speed brakes the revolution movement of the row of spherical rollers 3 with the higher revolution speed. In particular, this tendency becomes more significant in the case of operation while supporting an axial load. As a result, as described above, there is a possibility of a greater amount of dynamic torque and heat being generated due to operation.
Furthermore, also in the case of any one of the first to fourth examples of the conventional construction, the orientation of the spherical rollers 3 is not always stable in the pockets 9 of the retainers 4, and 4a to 4c. This is because the rolling surface of the spherical rollers 3 is a convex curved surface, whereas a sectional shape in the axial direction of the retainers 4 and 4a to 4c of the surface on both sides in the circumferential direction of the column sections 8a that constitute the surface on both sides in the circumferential direction of the pockets 9 is a straight line shape, parallel with this axial direction. Consequently, the outer peripheral surface, where the diameter is greatest, of the intermediate section in the axial direction of the spherical rollers 3 held in the respective pockets 9, makes contact with the surface on both sides in the circumferential direction of the column sections 8a, and a gap is formed between these surfaces on both sides in the circumferential direction and the portion close to both ends in the axial direction of the outer peripheral surface of the spherical rollers 3. Therefore, it becomes possible for these spherical rollers 3 to be displaced somewhat by oscillating centered around the contacting section of the intermediate section in the axial direction, to the extent of the above gap.
In the case where the spherical rollers 3 have been displaced by oscillating, so-called skewing occurs, in which the direction of the rotational axes of the spherical rollers 3 is at an inclined angle with respect to the direction orthogonal to the direction of revolution of these spherical rollers 3. When such skewing has occurred, significant sliding friction occurs at the rolling contact portion between the rolling surface of the spherical rollers 3 and the outer raceway 5 and the inner raceways 6. Consequently, not only does the resistance required for relative rotation between the outer ring 1 and the inner ring 2 (dynamic torque of the self-aligning roller bearing) become greater, but vibration generated in the respective rolling contact portions also becomes greater. Such increased dynamic torque and occurrence of vibration are not regarded as a significant problem when the operation speed of the self-aligning roller bearing is low. However, in order to increase this operation speed, it is necessary to stabilize the orientation of the spherical rollers 3 to suppress the occurrence of skewing in order to suppress dynamic torque and vibration.
Moreover, in the cases of the first, third, and fourth examples of the conventional construction shown in FIG. 17, FIG. 21, and FIG. 22, since the retainers 4, 4b, and 4c for holding both rows of spherical rollers 3 are positioned by inner ring riding or outer ring riding, a disadvantage in achieving high speed operation of the rotation shaft arises from the following points. Specifically, the relative speed (sliding velocity) between the inner peripheral surface of the rim section 7 and the outer peripheral surface of the inner ring 2 in the case of the fourth example of the conventional construction shown in FIG. 22, and the relative speed between the outer peripheral surface of the rim section 7 and the inner peripheral surface of the outer ring 1 in the case of the first and third examples of the conventional construction shown in FIG. 17 and FIG. 21, respectively become large in some cases. In this case, in the construction shown in FIG. 22, friction at the engaging section between the inner peripheral surface of the rim section 7 and the outer peripheral surface of the floating guide ring 16, and friction at the engaging section between the inner peripheral surface of the floating guide ring 16 and the outer peripheral surface of the inner ring 2 becomes greater, and in the construction shown in FIG. 17 and FIG. 21, friction at the engaging section between the outer peripheral surface of the rim section 7 and the inner peripheral surface of the outer ring 1 becomes greater. This results in a greater amount of dynamic torque (rotational resistance) and heat being generated due to operation of the self-aligning roller bearing with retainer, which becomes a disadvantage in high speed operation. Moreover, in the case of the construction shown in FIG. 22, the floating guide ring 16 is required to serve as an inner ring riding for the retainer 4, and the number of parts increases.
In order to solve the problems described above, controlling by so-called roller guiding is considered, by which the position in the radial direction of the retainer is controlled based on engagement between the inside surface of the pockets and the spherical rollers as shown in FIG. 20. However in the case of the self-aligning roller bearing with retainer, the retainer cannot be simply roller-guided for the following reason. For example, in the case of a general cylindrical roller bearing (cylindrical roller is not inclined with respect to the radial direction of the retainer), the rolling surface of the respective cylindrical rollers is the only part that engages with the inside surface of the respective pockets of the retainer as a result of displacement of the retainer in the radial direction. Therefore, in order to control the radial direction position of this retainer, it is sufficient to manage the clearance between the inside surface of the respective pockets and the rolling surface of the respective cylindrical rollers.
By contrast, in the self-aligning roller bearing with retainer, as shown in FIG. 17, FIG. 21, and FIG. 22, both rows of spherical rollers 3 held by the retainers 4, 4b, and 4c are arranged on an incline with respect to the radial direction of these retainers 4, 4b, and 4c. Therefore, in the case where these retainers 4, 4b, and 4c are displaced in the radial direction, the inside surface of the pockets 9 of these retainers 4, 4b, and 4c makes contact with either one of the rolling surface of the spherical rollers 3 or the end surface of the spherical rollers 3.
Moreover, in the case where the retainer is roller-guided, so-called skewing, in which the direction of the rotational axes of the respective spherical rollers is at an inclined angle with respect to the direction orthogonal to the direction of revolution of these spherical rollers, needs to be suppressed by the retainer. For example, in the case of the fourth example of the conventional construction shown in FIG. 22, the occurrence of skewing of the spherical rollers 3 is suppressed by the floating guide ring 16 and the rib section 10. Therefore, in this construction, in the case where the retainer is roller-guided and the floating guide ring 16 is omitted, skewing in the respective spherical rollers 3 needs to be suppressed by the rib section 10 and the retainer. Furthermore, as is the case with the third example of the conventional construction shown in FIG. 21, in the case of a construction where the rib section 10 is not formed, skewing of the spherical rollers 3 needs to be suppressed by the retainer only. Moreover, movement of the spherical rollers in the non-loaded zone, which is positioned on the side opposite to that where a load is applied to the self-aligning roller bearing with retainer, is controlled mainly by the retainer. Consequently, skewing may become more likely to occur to the spherical rollers in the non-loaded zone depending on the status of their engagement with the inside surface of the pocket of the retainer.
In the case where skewing of the spherical rollers 3 has occurred, a significant sliding friction occurs at the rolling contact portions between the rolling surfaces of the spherical rollers 3 and the outer raceway 5 and the inner raceways 6. Consequently, as the dynamic torque of the self-aligning roller bearing with retainer increases, the amount of heat generation increases, and furthermore, vibration occurring in the respective rolling contact portions becomes greater. An increase in such dynamic torque and heat generation and the occurrence of vibration is disadvantageous for increasing the operation speed of the self-aligning roller bearing with retainer.
Thus, in the case where the retainer of the self-aligning roller bearing with retainer is to be roller-guided, it is necessary to consider how to achieve positioning of the retainer in the radial direction (which of the inside surfaces of the respective pockets, and the rolling surface or the end surface of the spherical rollers are to be made to contact with each other) and furthermore, how to achieve suppression of skewing of the spherical rollers in the non-loaded zone. Therefore, the retainer that is assembled into the self-aligning roller bearing with retainer cannot be simply roller-guided.    Patent Document 1: Japanese Patent Application Publication No. H09-317760    Patent Document 2: Japanese Utility Model Registration No. 2524932